There's a company called S&G Enterprizes that specializes in compactors. They sell "Pak-More" hold-down disks. These are galvanized and corrosion- resistant, and have 3 each rubber flanges to grip the inside of the drum. They don't necessarily have to lodge in the drum-rings, and holds down spongy material really good. Their number is 800-233-3721 Conatser.Steven@Allen-Park.VA.GOV (313) 576-3595/3444